The present invention relates to an apparatus for preventing carriers from running out of control in a power-and-free conveyor.
Throughout the specification and the appended claims, the terms "front" or "forward" and "rear" or "rearward" are based on the direction of advance of the conveyor. Thus the term "front" or "forward" refers to the direction in which the conveyor advances, and the term "rear" or "rearward" to the opposite direction. The terms "right" and "left" are used when a person faces the forward direction.
Generally power-and-free conveyors have rising gradient sections and falling gradient sections. When a carrier is running into such a gradient section, it is likely that the drive chain will break or the free trolley will disengage from the power trolley. In such an event, the carrier will run out of control toward the descending direction along the gradient section. Accordingly there is the need to provide an apparatus for preventing runaway of carriers.
For the prevention of runaway in falling gradient sections of conveyors, an apparatus is known which comprises a runaway preventing member in an approximately T-shaped form and supported at its center portion by a horizontal pivot at the top of the power rail. The preventing member has opposite arms one of which serves as a trolley striking portion and the other as a trolley engaging portion. Another apparatus is known for use in rising gradient conveyor sections which comprises a plurality of moving members arranged along the direction of advance of the conveyor at a required spacing and movable along the rising gradient section, a retraction preventing stopper provided on each of the moving members for permitting only the advance of the trolley, means for coupling the moving member to an operative portion of a detector disposed at a required location, and a spring for biasing the moving member upward along the gradient section.
However, the former apparatus, which is designed for use in falling gradient sections, is not usable for rising gradient sections. Furthermore, depending on the location of the runaway preventing member, there is the likelihood that the apparatus will be unable to stop the foremost of runaway carriers. This must be eliminated by the use of a large number of runaway preventing members, which render the apparatus costly. The apparatus of the latter type is adapted for use in rising gradient sections and is not usable for falling gradient sections. The apparatus has the drawback that it is complex in construction, requires a large number of moving members and is therefore costly.